Introduction

As mentioned in the earlier post about omnilude-tools, a number of real tools in that project were backed by concrete PRD documents. The document published in this post is one of them: the Unix Timestamp Converter PRD.

This document was originally written in Korean to build the real timestamp-converter tool, and traces of that implementation still remain under src/app/[locale]/(tools)/developer/timestamp-converter/. In other words, this was not a loose idea memo. It was a working document that tied together screen structure, state management, SEO, and test design.

There are three points I especially want to make clear in this post.

This document is one of the PRDs used to build an actual tool inside omnilude-tools.
It is also a good real-world example of how the prd-generator skill can be used.
The original PRD was written in Korean, and for this post the full document is translated so that readers in each locale can read the entire text rather than a summary.

You can also access the live tool at tools.omnilude.com/developer/timestamp-converter.

If possible, I would have liked to share the prompt that was used to generate this PRD as well, but I deleted the session data because of disk space limitations, so I ask for your understanding that I cannot provide it here.

Main Body

In short, this document narrowed the scope down to a level where an implementer could move immediately.

What to build: a tool that converts between Unix timestamps and human-readable dates in both directions
How far to take it: MVP features, advanced features, timezones, live current time, code snippets, and a calculator
How to build it: file structure, Zustand state management, conversion utilities, SEO, tests, accessibility, and performance requirements
How to verify it: unit tests, E2E tests, and an implementation checklist

When a document reaches this level of detail, implementation becomes much simpler. The actual timestamp-converter page was built from this kind of structured guide, and it still remains as a developer tool inside omnilude-tools.

This document was translated from Korean

The source version for this post is a Korean PRD. For that reason, the translations in each locale focus on carrying the entire document across rather than reducing it to a short summary. Even though this is a PRD document, preserving the technical context and implementation background mattered more than shortening it.

Original PRD

Below is the full public version of the Unix Timestamp Converter PRD.

PRD: Unix Timestamp Converter

Basic Information

Item	Value
Tool ID	`timestamp-converter`
Group	`developer`
Path	`/developer/timestamp-converter`
Priority	P0 (Required)
Estimated Effort	1-2 days
Status	Draft

1. Overview

1.1 Purpose

A tool that provides two-way conversion between Unix timestamps and human-readable date formats.

1.2 Target Users

Backend and frontend developers
Data analysts
System administrators

1.3 Competitor Review

Site	Strengths	Weaknesses
epochconverter.com	Many formats, code snippets	Outdated UI
unixtimestamp.com	Simple UI	Limited features
timestamp-converter.com	Clean design	Limited timezone support

2. Functional Requirements

2.1 Core Features (MVP)

F1: Timestamp to Date Conversion

Typescript

Input: Unix timestamp (auto-detect seconds, milliseconds, or microseconds)
Output: Multiple date formats

Auto-detection logic:

Typescript

function detectTimestampUnit(value: number): 'seconds' | 'milliseconds' | 'microseconds' {
  if (value < 1e12) return 'seconds';       // fewer than 10 digits
  if (value < 1e15) return 'milliseconds';  // 13 digits
  return 'microseconds';                    // 16 digits
}

Output formats:

ISO 8601: 2026-01-29T13:45:30.000Z
RFC 2822: Wed, 29 Jan 2026 13:45:30 +0000
Local format: January 29, 2026, 10:45:30 PM
Relative time: 5 minutes ago, in 3 days

F2: Date to Timestamp Conversion

Typescript

Input: Date string or date picker
Output: Unix timestamp (seconds and milliseconds)

Supported input formats:

ISO 8601 string
Date and time picker (DatePicker)
Natural language (optional): now, yesterday, next week

F3: Timezone Support

Typescript

Default: Browser local timezone
Options: UTC and major city-based timezones

Major timezone list:

Typescript

const TIMEZONES = [
  { value: 'UTC', label: 'UTC' },
  { value: 'Asia/Seoul', label: 'Seoul (KST, UTC+9)' },
  { value: 'Asia/Tokyo', label: 'Tokyo (JST, UTC+9)' },
  { value: 'America/New_York', label: 'New York (EST/EDT, UTC-5/-4)' },
  { value: 'America/Los_Angeles', label: 'Los Angeles (PST/PDT, UTC-8/-7)' },
  { value: 'Europe/London', label: 'London (GMT/BST, UTC+0/+1)' },
  // ... add more
];

F4: Live Current Time Display

Typescript

Show the current Unix timestamp at the top of the screen and update it every second

2.2 Advanced Features

F5: Code Snippet Generation

Provide the selected timestamp as code in multiple programming languages.

Typescript

const CODE_SNIPPETS = {
  javascript: (ts: number) => `new Date(${ts * 1000})`,
  python: (ts: number) => `datetime.fromtimestamp(${ts})`,
  java: (ts: number) => `Instant.ofEpochSecond(${ts}L)`,
  go: (ts: number) => `time.Unix(${ts}, 0)`,
  php: (ts: number) => `date('Y-m-d H:i:s', ${ts})`,
  ruby: (ts: number) => `Time.at(${ts})`,
  csharp: (ts: number) => `DateTimeOffset.FromUnixTimeSeconds(${ts})`,
};

F6: Timestamp Calculator

Typescript

Base time + days/hours/minutes/seconds = result timestamp
Example: now + 7 days = timestamp for next week

3. UI/UX Design

3.1 Layout

┌─────────────────────────────────────────────────────────────┐
│  Current Unix Timestamp: 1738150800 (live update)  [Copy]  │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  ┌─────────────────────┐  ┌─────────────────────────────┐  │
│  │  Input              │  │  Result                     │  │
│  │                     │  │                             │  │
│  │  [Timestamp Input]  │  │  ISO 8601: ...      [Copy]  │  │
│  │  or                 │  │  RFC 2822: ...      [Copy]  │  │
│  │  [Date/Time Pick]   │  │  Local: ...         [Copy]  │  │
│  │                     │  │  Relative: ...      [Copy]  │  │
│  │  Timezone: [Pick ▼] │  │                             │  │
│  │                     │  │  Timestamp (s): ...         │  │
│  │  [Convert] [Clear]  │  │  Timestamp (ms): ...        │  │
│  └─────────────────────┘  └─────────────────────────────┘  │
│                                                             │
├─────────────────────────────────────────────────────────────┤
│  Code Snippets                                              │
│  ┌─────────────────────────────────────────────────────┐   │
│  │  [JS] [Python] [Java] [Go] [PHP] [Ruby] [C#]        │   │
│  │  ─────────────────────────────────────────────────  │   │
│  │  new Date(1738150800000)                   [Copy]   │   │
│  └─────────────────────────────────────────────────────┘   │
│                                                             │
└─────────────────────────────────────────────────────────────┘

3.2 Responsive Design

Desktop (lg+):

Two-column layout (input | result)

Tablet/Mobile (< lg):

One-column layout (input above, result below)

3.3 Interactions

Live conversion: Convert automatically on input (300ms debounce)
Copy feedback: Show a toast when the copy button is clicked
Keyboard shortcuts: Enter to convert, Ctrl+C to copy results

4. Technical Specification

4.1 File Structure

src/app/[locale]/(tools)/developer/timestamp-converter/
├── page.tsx                              # page entry + SEO
├── _store/
│   └── timestamp-store.ts                # Zustand state management
└── _components/
    ├── timestamp-page.tsx                # main client component
    ├── current-time-display.tsx          # current time display
    ├── timestamp-input.tsx               # input section
    ├── conversion-result.tsx             # result section
    └── code-snippets.tsx                 # code snippet section

4.2 State Management (Zustand)

Typescript

// _store/timestamp-store.ts
import { create } from 'zustand';

type InputMode = 'timestamp' | 'datetime';

interface TimestampState {
  // input
  inputMode: InputMode;
  timestampInput: string;
  dateInput: Date | null;
  timezone: string;

  // result
  result: ConversionResult | null;

  // code snippets
  selectedLanguage: string;

  // actions
  setInputMode: (mode: InputMode) => void;
  setTimestampInput: (value: string) => void;
  setDateInput: (date: Date | null) => void;
  setTimezone: (tz: string) => void;
  setSelectedLanguage: (lang: string) => void;
  convert: () => void;
  clear: () => void;
}

interface ConversionResult {
  timestampSeconds: number;
  timestampMillis: number;
  iso8601: string;
  rfc2822: string;
  localFormat: string;
  relative: string;
}

export const useTimestampStore = create<TimestampState>((set, get) => ({
  inputMode: 'timestamp',
  timestampInput: '',
  dateInput: null,
  timezone: Intl.DateTimeFormat().resolvedOptions().timeZone,
  result: null,
  selectedLanguage: 'javascript',

  setInputMode: (mode) => set({ inputMode: mode }),
  setTimestampInput: (value) => set({ timestampInput: value }),
  setDateInput: (date) => set({ dateInput: date }),
  setTimezone: (tz) => set({ timezone: tz }),
  setSelectedLanguage: (lang) => set({ selectedLanguage: lang }),

  convert: () => {
    const { inputMode, timestampInput, dateInput, timezone } = get();
    // conversion logic
  },

  clear: () => set({
    timestampInput: '',
    dateInput: null,
    result: null,
  }),
}));

4.3 Core Conversion Logic

Typescript

// lib/timestamp-utils.ts
import { format, formatDistanceToNow } from 'date-fns';
import { formatInTimeZone } from 'date-fns-tz';
import { ko, en, ja } from 'date-fns/locale';

export function convertTimestamp(
  timestamp: number,
  timezone: string,
  locale: string
): ConversionResult {
  // auto-detect unit
  const unit = detectTimestampUnit(timestamp);
  const timestampMs = unit === 'seconds'
    ? timestamp * 1000
    : unit === 'microseconds'
      ? Math.floor(timestamp / 1000)
      : timestamp;

  const date = new Date(timestampMs);
  const localeObj = { ko, en, ja }[locale] || ko;

  return {
    timestampSeconds: Math.floor(timestampMs / 1000),
    timestampMillis: timestampMs,
    iso8601: date.toISOString(),
    rfc2822: format(date, 'EEE, dd MMM yyyy HH:mm:ss xx', { locale: localeObj }),
    localFormat: formatInTimeZone(date, timezone, 'PPpp', { locale: localeObj }),
    relative: formatDistanceToNow(date, { addSuffix: true, locale: localeObj }),
  };
}

export function dateToTimestamp(date: Date): { seconds: number; millis: number } {
  const millis = date.getTime();
  return {
    seconds: Math.floor(millis / 1000),
    millis,
  };
}

4.4 Dependencies

JSON

{
  "dependencies": {
    "date-fns": "^3.x",
    "date-fns-tz": "^3.x"
  }
}

Already installed in the project.

5. Internationalization Support

5.1 Translation Keys

JSON

// messages/en/tools/developer/timestamp-converter.json
{
  "tools": {
    "developer": {
      "timestampConverter": "Timestamp Converter",
      "timestampConverterDesc": "Convert between Unix timestamps and dates",
      "timestamp": {
        "currentTime": "Current Unix Timestamp",
        "inputTimestamp": "Timestamp Input",
        "inputDatetime": "Date/Time Input",
        "timezone": "Timezone",
        "convert": "Convert",
        "clear": "Clear",
        "copy": "Copy",
        "copied": "Copied",
        "results": "Conversion Results",
        "iso8601": "ISO 8601",
        "rfc2822": "RFC 2822",
        "localFormat": "Local Format",
        "relative": "Relative Time",
        "timestampSeconds": "Timestamp (seconds)",
        "timestampMillis": "Timestamp (milliseconds)",
        "codeSnippets": "Code Snippets",
        "invalidTimestamp": "Invalid timestamp",
        "autoDetected": "Auto-detected: {unit}"
      }
    }
  }
}

6. SEO Metadata

Typescript

// page.tsx
export async function generateMetadata({ params }: Props): Promise<Metadata> {
  const { locale } = await params;
  const t = await getTranslations({ locale });

  return generateSeoMetadata({
    locale,
    title: t('tools.developer.timestampConverter'),
    description: t('tools.developer.timestampConverterDesc'),
    path: '/developer/timestamp-converter',
    keywords: [
      'unix timestamp',
      'epoch converter',
      'timestamp converter',
      'date conversion',
      'timestamp to date',
      'date to timestamp',
    ],
  });
}

7. Test Cases

7.1 Unit Tests

Typescript

describe('detectTimestampUnit', () => {
  it('should detect seconds', () => {
    expect(detectTimestampUnit(1738150800)).toBe('seconds');
  });

  it('should detect milliseconds', () => {
    expect(detectTimestampUnit(1738150800000)).toBe('milliseconds');
  });

  it('should detect microseconds', () => {
    expect(detectTimestampUnit(1738150800000000)).toBe('microseconds');
  });
});

describe('convertTimestamp', () => {
  it('should convert timestamp to ISO 8601', () => {
    const result = convertTimestamp(1738150800, 'UTC', 'en');
    expect(result.iso8601).toBe('2025-01-29T09:00:00.000Z');
  });
});

7.2 E2E Test

Typescript

test('timestamp conversion flow', async ({ page }) => {
  await page.goto('/en/developer/timestamp-converter');

  // enter timestamp
  await page.fill('[data-testid="timestamp-input"]', '1738150800');

  // verify result
  await expect(page.locator('[data-testid="iso8601-result"]'))
    .toContainText('2025-01-29');

  // click copy button
  await page.click('[data-testid="copy-iso8601"]');
  await expect(page.locator('.toast')).toContainText('Copied');
});

Introducing Some of the PRD Documents Used to Build omnilude-tools

Introduction

Main Body

This document was translated from Korean

Original PRD

PRD: Unix Timestamp Converter

Basic Information

1. Overview

1.1 Purpose

1.2 Target Users

1.3 Competitor Review

2. Functional Requirements

2.1 Core Features (MVP)

F1: Timestamp to Date Conversion

F2: Date to Timestamp Conversion

F3: Timezone Support

F4: Live Current Time Display

2.2 Advanced Features

F5: Code Snippet Generation

F6: Timestamp Calculator

3. UI/UX Design

3.1 Layout

3.2 Responsive Design

3.3 Interactions

4. Technical Specification

4.1 File Structure

4.2 State Management (Zustand)

4.3 Core Conversion Logic

4.4 Dependencies

5. Internationalization Support

5.1 Translation Keys

6. SEO Metadata

7. Test Cases

7.1 Unit Tests

7.2 E2E Test

8. Accessibility Requirements

9. Performance Requirements

10. Implementation Checklist

Introduction#

Main Body#

This document was translated from Korean#

Original PRD#

PRD: Unix Timestamp Converter#

Basic Information#

1. Overview#

1.1 Purpose#

1.2 Target Users#

1.3 Competitor Review#

2. Functional Requirements#

2.1 Core Features (MVP)#

F1: Timestamp to Date Conversion#

F2: Date to Timestamp Conversion#

F3: Timezone Support#

F4: Live Current Time Display#

2.2 Advanced Features#

F5: Code Snippet Generation#

F6: Timestamp Calculator#

3. UI/UX Design#

3.1 Layout#

3.2 Responsive Design#

3.3 Interactions#

4. Technical Specification#

4.1 File Structure#

4.2 State Management (Zustand)#

4.3 Core Conversion Logic#

4.4 Dependencies#

5. Internationalization Support#

5.1 Translation Keys#

6. SEO Metadata#

7. Test Cases#

7.1 Unit Tests#

7.2 E2E Test#

8. Accessibility Requirements#

9. Performance Requirements#

10. Implementation Checklist#

Introduction

Main Body

This document was translated from Korean

Original PRD

PRD: Unix Timestamp Converter

Basic Information

1. Overview

1.1 Purpose

1.2 Target Users

1.3 Competitor Review

2. Functional Requirements

2.1 Core Features (MVP)

F1: Timestamp to Date Conversion

F2: Date to Timestamp Conversion

F3: Timezone Support

F4: Live Current Time Display

2.2 Advanced Features

F5: Code Snippet Generation

F6: Timestamp Calculator

3. UI/UX Design

3.1 Layout

3.2 Responsive Design

3.3 Interactions

4. Technical Specification

4.1 File Structure

4.2 State Management (Zustand)

4.3 Core Conversion Logic

4.4 Dependencies

5. Internationalization Support

5.1 Translation Keys

6. SEO Metadata

7. Test Cases

7.1 Unit Tests

7.2 E2E Test

8. Accessibility Requirements

9. Performance Requirements

10. Implementation Checklist